1. Field of the Invention
The present invention relates to a white polyester film for use of a laminate with a metal plate excellent in heat resistance, wet heat resistance and forming property, and more specifically to a white polyester film suitable to use for forming after heat bonding it to a metal.
2. Description of the Related Art
Various white polyester films have been known. For example,
(A) a film wherein copolymerization components are controlled in the range of 2 to 50 mol % and inorganic additives are added at a content of 1 to 20% by weight (for example, JP-A-SHO 52-13542), PA0 (B) a film wherein the heat of crystalline melting is suppressed not more than 6.0 cal/g and white inorganic particles are added at a content of 5 to 30% by weight (for example, JP-A-HEI 1-241492), and PA0 (C) a film added with particles having a particle diameter of 0.1 to 25 .mu.m by a number of about 1.times.10.sup.8 / mm.sup.3 whose melting point is in the range of 210.degree. to 245.degree. C. (for example, JP-A-HEI 5-170942), are known. In such white films of the above-described (A), (B) and (C), however, because the heat resistance and the wet heat resistance thereof are poor, they cannot be sufficiently served to practical uses, particularly to uses wherein the films are heat bonded and formed and thereafter the metal-film laminates are heated. PA0 1 treatment by silane coupling agent or isopropyltitanate PA0 2 hydrophobic treatment by an organic compound after treatment by two or more kinds of hydrate oxides